The Trimble 4700 Site Surveyor is an example of a GPS land survey instrument that is similar to the present invention. Similar products are available from other GPS manufacturers. The 4700 Site Surveyor has a staff with a GPS antenna at the top end and a simple spike at the bottom end. A hand-held control and display unit (CDU) can be alternatively held by the surveyor or mounted to the staff at the approximate midpoint. Modern GPS receivers for surveying are small enough to be mounted to the staff as well. Alternatively the receiver can be carried with the batteries that power the unit in a backpack carried by the surveyor. The surveyor walks to each point to be surveyed, places the spike at the bottom end on the point, and either records a position computed by the receiver or “occupies” the point for a period of time during which the receiver records data for post-survey processing.
The disclosed Walking Stick Navigator (WSN) is designed to have the “look and feel” of a typical GPS survey instrument. It is believed that the WSN will gain acceptance among surveyors fairly quickly because of its similarity to industry accepted GPS survey instruments. The only additional field procedure that a surveyor must conduct is to manipulate the WSN like a walking stick when GPS drops out.
In operation, the surveyor uses the WSN for dead reckoning navigation when GPS signals become obstructed, as might occur inside or between buildings or in a forested area. The surveyor walks a survey trajectory and uses the WSN as a positioning system to survey positions along the trajectory. Such survey trajectories sometimes pass through areas where no GPS signals are available. The WSN must therefore navigate in a dead-reckoning mode with as little position drift as possible.